//khodaya khodet komak kon
#include <bits/stdc++.h>
#define F first
#define S second
#define pb push_back
#define all(x) x.begin(), x.end()
#pragma GCC optimize ("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize ("-O2")
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
const int N = 500000 + 10;
const ll MOD = 1000000000 + 7;
const ll INF = 1000000000000000010;
const ll LOG = 25;
struct per{
ll a, b;
};
ll seg[N << 2], lazy[N << 2], n;
per A[N];
void modify(int id, ll x){
seg[id] += x;
lazy[id] += x;
}
void shift(int id){
modify(id << 1, lazy[id]);
modify(id << 1 | 1, lazy[id]);
lazy[id] = 0;
}
void add(int id, int lq, int rq, ll x, int l, int r){
if (rq <= l || r <= lq)return;
if (lq <= l && r <= rq){
modify(id, x);
return;
}
int md = (l +r) >> 1;
shift(id);
add(id << 1, lq, rq, x, l, md);
add(id << 1 | 1, lq, rq, x, md, r);
seg[id] = max(seg[id << 1], seg[id << 1 | 1]);
}
bool cmp(per x, per y){
return x.a < y.a;
}
int32_t main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n;
for (int i = 1; i <= n; i++){
cin >> A[i].a >> A[i].b;
}
sort(A + 1, A + n + 1, cmp);
ll ans = 0;
for (int i = 1; i <= n; i++){
add(1, i, n + 1, A[i].b, 1, n + 1);
add(1, i, i + 1, -A[i].a, 1, n + 1);
}
for (int i = 1; i <= n; i++){
add(1, i, n + 1, A[i].a, 1, n + 1);
ans = max(ans, seg[1]);
add(1, i, n + 1, -A[i].b, 1, n + 1);
add(1, i, n + 1, -A[i].a, 1, n + 1);
}
cout << ans;
return 0;
}
